This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-313049, filed Oct. 28, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a semiconductor device that includes a plurality of capacitors having different capacities. More specifically, the invention relates to a semiconductor device that includes an improved RF (radio frequency) capacitor having an MIM (metal-insulator-metal) structure.
2. Description of the Related Art
RF MIM capacitors are elements essential for embedding an analog circuit and a digital CMOS circuit on a single chip. Recently, it has been proposed to use a high dielectric film, such as a Ta2O5 film, as a capacitor insulation film in order to reduce the area of the occupation of MIM capacitors (Jpn. Pat. Appln. KOKAI Publication No. 2001-177057).
The high dielectric MIM capacitor using a Ta2O5 film or the like has the same capacity as that of a conventional one though its area is small, whereas it has a drawback of increasing a leakage current. This drawback is caused for the following reason. Because of oxidation of the surface of a lower electrode and reaction with the material thereof at the time of formation of a Ta2O5 film, oxygen deficiencies due to a plasma atmosphere at the time of formation of an upper electrode, and the like, a leakage current flowing through the Ta2O5 film becomes difficult to control.
Some capacitors used for a semiconductor device require a large capacity, and others do a small leakage current rather than a large capacity. It is thus likely that when Ta2O5 is used in a capacitor insulation film, it will not meet the requirement that the leakage current should be small. The above-described problem will be solved if a capacitor using high dielectric materials and a capacitor having a small leakage current are manufactured separately from each other; however, manufacturing costs for the device will increase remarkably.
The use of a capacitor insulation film having a high dielectric constant has conventionally been considered in order to reduce the area of capacitors. Since, however, such a capacitor insulation film increases a leakage current, it is inapplicable to a capacitor that requires a small leakage current. Moreover, the separate manufacturing of a capacitor using high dielectric materials and a capacitor having a small leakage current causes an upswing in manufacturing costs.
According to an aspect of the present invention, there is provided a semiconductor device including a plurality of capacitors, comprising:
a first capacitor arranged on a substrate and including first upper and lower electrode layers between which a first capacitor insulation film is interposed; and
a second capacitor arranged on the substrate and including second upper and lower electrode layers between which a second capacitor insulation film is interposed, the second upper and lower electrode layers having a same structure as that of the first upper and lower electrode layers, and the second capacitor having a per-unit-area capacity different from that of the first capacitor.
According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device including a plurality of capacitors, comprising:
forming a lower conductive film on a semiconductor substrate, the lower conductive film serving as a lower electrode;
forming a capacitor insulation film on the lower conductive film, the capacitor insulation film including one of a single layer and a multilayer dielectric layer and partly varying in one of material and structure;
forming an upper conductive film on the capacitor insulation film, the upper conductive film serving as an upper electrode;
forming a lower electrode by etching the upper conductive film and then the lower conductive film into a lower electrode pattern; and
forming an upper electrode by etching the upper conductive film into an upper electrode pattern.